面试技术问询：$q.all方法的正确使用语法有哪些？

Let's break down each option to figure out which are valid uses of $q.all():

• First option (array of promises):

  $q.all([promise1(), promise2()]).then((values) => { … });
  

  This is valid. $q.all() accepts an array of promise instances (or calls to promise-returning functions, since invoking them returns a promise). The .then() callback will receive an array of resolved values, ordered to match the input promises.

• Second option (individual arguments):

  $q.all("promise1", "promise2").then((values) => { … });
  

  This is invalid. $q.all() doesn't accept multiple standalone arguments—it expects either a single array or a single object as its only parameter. On top of that, passing string literals here is meaningless, since they aren't promises.

• Third option (object of promises):

  $q.all({"promise1": promise1(), "promise2": promise2()}).then((values) => { ... });
  

  This is valid. $q.all() also supports an object where each property maps to a promise (or a call to a promise-returning function). The .then() callback will receive an object with the same keys, each mapped to their corresponding resolved value.

To sum up: the first and third options are the correct syntax for $q.all().

内容的提问来源于stack exchange，提问作者Rorbert Gilbert